Petrol models
In order to reduce the emission of toxic components into the atmosphere that enter the composition of the exhaust gases of the engine as a result of evaporation and incomplete combustion of fuel, as well as to maintain engine efficiency and reduce fuel consumption, the gasoline models discussed in this manual are equipped with a number of special systems that can be would be merged under a common name engine management systems and exhaust emissions reduction.
Systems related to engine management and emission control include the following:
- On-Board Diagnostic System (OBD), - see Chapter Engine electrical equipment;
- Electronic engine management system - see Chapter Engine electrical equipment;
- Controlled crankcase ventilation system (PCV);
- Exhaust gas recirculation system (EGR);
- Evaporative Emission System (EVAP);
- Catalytic converter and lambda probe (exhaust gas composition control).
The functioning of all these systems, one way or another, directly or indirectly, is related to the management of the reduction of exhaust gas toxicity.
The following Sections provide general descriptions of how each system operates, as well as procedures for diagnostic checks and remedial repairs (if it is possible) components of systems, the performance of which lies within the qualifications of the average amateur mechanic.
Before coming to the conclusion that any of the emission control systems have failed, carefully check the power and ignition systems for proper functioning (see chapters Power and exhaust systems and Engine electrical equipment). Diagnostics of some of the components of toxicity reduction systems requires the use of special, difficult-to-use equipment and a certain qualification of the performer, and therefore, it would be reasonable to entrust its implementation to professional mechanics of a specialized service station.
The foregoing does not mean that the maintenance and repair of components of toxicity reduction systems in practice seem difficult. Do not forget that one of the most common causes of failures is an elementary violation of the quality of vacuum or electrical connections, and therefore, first of all, you should always check the condition of the fittings and electrical connectors. The car owner can independently and quite simply carry out a number of checks, as well as perform many routine maintenance procedures for most system components at home, using the usual set of tuning and locksmith tools.
Be aware of additional federal warranties that apply to emission control and engine management components. Before proceeding with any procedures for the repair of components and parts of these systems, consult the conditions for compliance with these obligations at the representative office of Opel.
Try to observe all the precautions specified in the following Sections when performing maintenance of the electronic components of the systems in question. It should be noted that the illustrative material may not always exactly match the actual placement of components on the vehicle. Such inconsistencies are associated with the ongoing process of modification within the framework of the typical design of each model.
An information label of exhaust gas toxicity reduction systems is fixed in the engine compartment of the car (VECI). The label contains the necessary information on the settings and checks of controlled systems, taking into account all modifications made to a particular vehicle, as well as a diagram of the laying of vacuum hoses with the identification of various components. Read the VECI data carefully before servicing the emission control and engine management systems.
Crankcase ventilation system (PCV)
The PCV system is used to reduce the emission of hydrocarbon compounds into the atmosphere by removing crankcase gases from the engine. The unit is purged by forcing fresh air coming from the air cleaner through the crankcase, where it mixes with accumulated fumes and gases escaping from the combustion chambers and is discharged through the PCV valve into the intake manifold.
The main components of the system are the PCV valve, the purge filter and the set of vacuum hoses connecting these devices to the engine.
In order to maintain stable idle speed, the PCV valve shuts off the purge flow when the vacuum in the intake manifold is deep. In the event of a malfunction of the engine (such as worn piston rings) the system removes excess crankcase gases through the ventilation tube back to the air cleaner.
Exhaust gas monitoring
In order to minimize the emission of toxic components into the atmosphere, a catalytic converter is included in the exhaust gas system. The control is carried out by a closed type control system. Feedback from the ECM is organized by means of a lambda probe mounted in the downpipe of the exhaust system.
The catalytic converter is a component of exhaust gas toxicity reduction systems, is included in the exhaust system and serves to reduce the emission of toxic components into the atmosphere. The vehicles covered in this manual use two types of catalytic converters. A conventional oxidizing converter can reduce the content of hydrocarbons and carbon monoxide in the exhaust gases. Tri-functional catalytic converter further reduces nitrogen oxide emissions (NO x).
Lambda probe (oxygen sensor) monitors the oxygen content in the exhaust gas stream. When O 2 molecules come into contact with the sensitive element of the probe, the sensor generates an amplitude signal in the range from 0.1 to 0.9 V, depending on the oxygen concentration. Moreover, a value of 0.1 V corresponds to a high content of O 2 (lean mixture), and a value of 0.9 V - low (rich mixture). The ECM continuously monitors the signals coming from the lambda probe, if necessary, issuing commands to adjust the composition of the air-fuel mixture by changing the duration of the opening of the injection injectors. The optimal ratio of the components of the combustible mixture, which guarantees the minimum fuel consumption with the most efficient functioning of the catalytic converter, is 14.7 parts of air per 1 part of the fuel, which is what the control module tries to constantly maintain, focusing on the information coming from the lambda probe. On the car models in question, two lambda probes are used; the primary is located in the exhaust manifold of the engine, and the secondary is located below the catalytic converter. By comparing the level of oxygen in the areas of the exhaust tract above and below the catalytic converter, the ECM also determines the effectiveness of the functioning of the latter.
It should be noted that the lambda probe is capable of generating a signal voltage only when warmed up to normal operating temperature (about 320°C). While the sensor is cold, the ECM operates in OPEN LOOP mode.
In the event of a malfunction of the lambda probe or its circuit, the ECM goes into emergency mode (open loop mode), ignoring the information coming from the sensors and maintaining the composition of the air-fuel mixture at a certain predetermined level, which ensures sufficient efficiency of the engine output.
The correct functioning of the lambda probe depends on the fulfillment of a combination of certain specific conditions:
- Electrical parameters: The stability of the low voltage amplitude signal generated by the sensor largely depends on the quality of the contact connections of the lambda probe circuit, which should be checked first of all in case of problems;
- Outside air supply: The design of the lambda probe provides for the free circulation of outside air inside the sensor. When installing the probe, always check the patency of the air channels;
- Working temperature: ECM begins to respond to information from the lambda probe only after the sensor has warmed up to normal operating temperature (about 320°C). This fact should not be overlooked when checking the correct operation of the probe;
- Fuel quality: The correct functioning of the lambda probe becomes possible only if UNLEADED fuel is used for refueling the car!
Evaporative Emission System (EVAP)
The system accumulates fuel vapors accumulating in the power supply system while the vehicle is parked and ensures that they are discharged into the intake pipeline for combustion during the normal operation of the engine.
Any EVAP system necessarily includes a special adsorber filled with activated carbon, which, in fact, collects fuel vapors. The method of removing vapor from the adsorber may vary depending on the design of a particular system. The following description will allow the reader to understand in sufficient detail the principles of operation of any type of EVAP system.
The described design does not necessarily have to fully correspond to the design of the system installed on a particular vehicle, however, the principle of operation is common to all models equipped with a fuel injection system. If any deviations are found, check the information given on the VECI label attached under the hood.
The fuel filler cap is equipped with a two-way safety valve. In the event of a system failure, the valve ensures that fuel vapors are vented to the atmosphere.
Other check valve (ORVR valve) installed near the fuel tank and provides adjustment of fuel vapor removal to the carbon adsorber depending on pressure/vacuum drops associated with temperature changes.
On the way to the carbon adsorber, fuel vapors are passed through a two-way valve and through the ventilation hoses they enter the carbon adsorber installed in the engine compartment, where they are accumulated during the entire parking time.
When the engine is started until it warms up to a certain temperature, the canister purge shut-off solenoid valve remains closed, allowing the purge diaphragm valve to open due to an increase in the depth of vacuum in the intake piping. From the adsorber, fuel vapors are blown out through the diaphragm valve into the intake manifold, from where they enter the combustion chambers, where they are burned out during the normal operation of the engine.
The fuel tank is also usually equipped with a sensor that monitors pressure changes in the tank both while the vehicle is stationary and while the vehicle is moving.
Exhaust gas recirculation system (EGR)
In order to reduce the emission of nitrogen oxides into the atmosphere, the engine design provides for the removal of part of the exhaust gases into the intake pipeline through the EGR valve. This admixture of exhaust gases to the air-fuel mixture leads to a decrease in its combustion temperature.
The system consists of an EGR valve, an EGR valve opening degree sensor, a control module (ECM) and a set of auxiliary information sensors. The ECM is programmed to provide the optimum EGR valve opening for all engine operating conditions. A special information sensor constantly monitors the degree of opening of the EGR valve, issuing appropriate signals to the control module. The ECM compares the incoming sensor information with the optimal calculated value determined from data from other information sensors and, if necessary, makes the required adjustment of the amount of exhaust gases entering the engine.
On models 1.4, 1.6 and 1.8 l an electric EGR valve is used, mounted on the intake manifold, or on the left side of the cylinder head. On engines 2.0 l uses an EGR solenoid valve assembly placed on the cylinder head.
Diesel models
On diesel models, the overall control of the composition of the exhaust gases is also carried out by the engine control module (ECM). The main goal is the same as for gasoline models - to obtain maximum engine efficiency at minimum cost, combined with minimizing the emission of toxic constituents of combustion products into the atmosphere.
The solution of the problem is carried out by three main systems: crankcase ventilation system (PCV), exhaust gas recirculation system (EGR) and a catalytic converter.
Controlled crankcase ventilation system (PCV)
The principle of operation of the PCV system is completely similar to that described above for gasoline engines.
Exhaust gas monitoring
The main element of the control system is a catalytic converter that provides additional oxidation of carbon monoxide (SO), - see above.
Exhaust gas recirculation system (EGR)
The principle of operation of the EGR system is similar to that described above for gasoline engines. The EGR vacuum valve is located at the top of the intake manifold and is actuated by commands from the ECM to the control solenoid.
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